Research finds new insights into how our olfactory sense works

December 23rd, 2008 - 3:26 pm ICT by IANS  

Washington, Dec 23 (IANS) “A rose by any other name would smell as sweet,” wrote Shakespeare. But would it if the molecules that generate its fragrance were to shift shape? That’s what Kevin Ryan, assistant professor of chemistry at The City College of New York (CCNY) and collaborators in the lab of Stuart Firestein, professor of biology at Columbia University, set out to investigate.

Their findings offer new insight into how our sense of smell works and have potential applications in the design of flavours and fragrances.

When odour-producing molecules, known as odorants, pass through the nose, they trigger intracellular changes in a subset of the approximately 400 different varieties olfactory sensory neurons (OSN) in the nose’s internal membrane tissue, Ryan explained.

The unique reaction pattern produced, known as the olfactory code, is sent as a signal to the brain, which leads to perception of odours.

Ryan and his team wanted to learn how these receptor cells respond when odorants change their shape. They studied the odorant octanal, an eight-carbon aldehyde that occurs in many flowers and citrus fruits.

Octanal is a structurally flexible molecule that can adapt to many different shapes by rotating its chemical bonds, said a CCNY release.

The researchers designed and synthesized eight-carbon aldehydes that resembled octanal, but had their carbon chains locked by adding one additional bond.

These molecules were tested on genetically engineered OSNs known to respond to octanal. This work was done in Firestein’s lab at Columbia.

The aldehyde molecules that could stretch to their greatest length triggered strong activity in the OSNs. However, those molecules whose carbon chains were constrained into a U-shape blocked the receptor and left the cell unable to sense octanal.

Ryan noted that “the results indicate that these odorant molecules might be able to alter fragrance mixture odours in two ways: by muting the activity of flexible odorants present in a mixture and by activating a smaller subset of OSNs than chemically related flexible odorants. This would produce a different olfactory code signature.”

These findings were published in the journal Chemistry & Biology.

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